Position detection of blood pressure device

ABSTRACT

An aspect of the disclosure pertains to detecting a position of a blood pressure measurement device. An inflatable bladder of the blood pressure measurement device defines, at least in part, a pressurizable volume. The inflatable bladder may be inflated to pressurize a user&#39;s appendage and temporarily occlude blood flow in the user&#39;s appendage. A pump may initiate inflation of the inflatable bladder when one or more accelerometers and/or one or more proximity sensors determine that the blood pressure measurement device is within sufficient proximity or elevation to a user&#39;s heart and stationary.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 to U.S. patent application Ser. No. 15/855,932,filed Dec. 27, 2017, titled “FINGER BLOOD PRESSURE CUFF,” which, inturn, claims the benefit of priority under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application No. 62/566,202, filed Sep. 29, 2017, andtitled “FINGER BLOOD PRESSURE CUFF,” each of which is herebyincorporated by reference herein in its entirety and for all purposes.

INTRODUCTION

Blood pressure is an important health indicator measured in bothclinical and nonclinical settings. Many automated systems for measuringa user's blood pressure may use an oscillometric blood pressuremeasurement (OBPM) technique. Traditional OBPM systems inflate a bladderwith air and squeeze an artery with a varying amount of pressure, andthe OBPM systems “listen” for the strength of user's heart beat againstthat pressure. OBPM systems are widely used, primarily because they areeasier to use than other alternative methods and do not require atrained operator as compared to the traditional ausculatory method.

The pressure signal captured by OBPM is affected by hydrostaticpressure, which is affected by cuff placement relative to the heart.Some existing OBPM systems require placement of the measuring devicearound the upper arm at the heart level to cause the hydrostaticpressure to be nearly equivalent to the hydrostatic pressure at theheart. Other existing OBPM systems can be placed around the wrist, butsuch OBPM systems may be more susceptible to variations in hydrostaticpressure, e.g., due to elevation differences between the heart and themeasurement location.

Arm cuff OBPM systems tend to be large, cumbersome, and uncomfortable.Wrist-worn OBPM systems may be more portable but tend to be lessreliable and less accurate than arm cuff OBPM systems.

SUMMARY

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims.

One aspect of the disclosure relates to a device for estimating a user'sblood pressure. The device includes a housing having a hole sized toreceive a human finger, a pump, an inflatable elastic bladder disposedabout an inward-facing surface of the hole and defining, at least inpart, a pressurizable volume in fluidic communication with the pump, anda pressure sensor in fluidic communication with the pressurizable volumeand configured to produce pressure data indicative of a pressure withinthe pressurizable volume as a function of time. The pump is configuredto pressurize the pressurizable volume and cause the inflatable elasticbladder to expand towards the center of the hole and contact a user'sfinger when the user's finger is positioned in the opening of the deviceand the pump is activated.

In some implementations, the device further includes a ring-shapedstructure disposed within the hole and encircling the inflatable elasticbladder, the ring-shaped structure further defining, at least in part,the pressurizable volume. The ring-shaped structure may have a first endand a second end with a substantially cylindrical inner surface spanningbetween the first end and the second end, the inflatable elastic bladderincluding a first seal bead and a second seal bead with a membranestructurally interposed between the first seal bead and the second sealbead, the first seal bead being sealed against the first end of thering-shaped structure and the second seal bead being sealed against thesecond end of the ring-shaped structure, the ring shaped structureincluding one or more ports that fluidically connect the pressurizablevolume with the pump. The one or more ports may pass through thering-shaped structure and may be configured to fluidically connect thepressurizable volume with an annular passage encircling the ring-shapedstructure and in fluidic communication with the pump. In someimplementations, the pressurizable volume has a continuous annularshape. In some implementations, the inflatable elastic bladder includestwo or more lobes substantially symmetrically distributed about a centeraxis of the hole, each lobe including a middle portion bracketed betweentwo end portions, the middle portion of each lobe extending closer tothe center axis than the corresponding end portions of that lobe whenthe pressurizable volume is at zero gauge pressure. The device mayfurther include a controller that is configured to control the pump toincrease the pressure within the pressurizable volume from a firstpressure to a second pressure, thereby causing the inflatable elasticbladder to expand towards the center axis, and to cause a notificationto be provided indicating that the user should insert their finger intothe hole responsive to an indication from the pressure sensor that thepressurizable volume is at the second pressure, that is configured tocontrol the pump to further increase the pressure in the pressurizablevolume beyond the second pressure, that is configured to monitor thepressure data from the pressure sensor to determine when the pressurewithin the pressurizable volume reaches a third pressure at whichpulsatile variations in the pressure within the pressurizable volume aredetectable in the pressure data, that is configured to control the pumpto further increase the pressure in the pressurizable volume to a fourthpressure at which the pulsatile variations in the pressure within thepressurizable volume decrease to a first predetermined level, that isconfigured to determine systolic blood pressure data based on the fourthpressure, and that is configured to determine diastolic blood pressuredata based on the third pressure. The inflatable elastic bladder mayhave a helical twist about the center axis of the hole. In someimplementations, the inflatable elastic bladder is made of silicone orother elastomer having a Young's modulus selected from a groupconsisting of: between about 0.001 GPa to about 0.1 GPa and betweenabout 0.003 GPa and about 0.05 GPa. In some implementations, theinflatable elastic bladder includes a membrane section that transitionsto a bellows section at opposing ends, each bellows section extendingback towards the other bellows section from where that bellows sectiontransitioned to the membrane section, each bellows section terminatingin a seal bead that encircles the membrane section. In someimplementations, the housing includes a circumferential lip that extendsaround the hole, forms an aperture smaller than the hole when viewedalong a center axis of the hole, and obscures a portion of theinflatable elastic bladder from view when viewed along the center axiswith the device oriented such that the inflatable elastic bladder isbehind the circumferential lip.

Another aspect of the disclosure relates to a device for estimating auser's blood pressure. The device includes an inflatable bladderdefining, at least in part, a pressurizable volume, a pump in fluidiccommunication with the inflatable bladder and configured to pressurizethe pressurizable volume and cause the inflatable bladder to inflate andcontact a user's appendage when the pump is activated, and a pressuresensor in fluidic communication with the inflatable bladder andconfigured to produce pressure data indicative of pressure within thepressurizable volume as a function of time. An inflation rate of thepump is controllable by controlling at least one of a duty cycle, avoltage, or a drive frequency.

In some implementations, the inflatable bladder is an inflatable elasticbladder disposed about an inward-facing surface of a hole in the device,where the pump is configured to pressurize the pressurizable volume whena user's finger is positioned in the hole of the device. In someimplementations, the inflation rate of the pump is controlled to bebetween about 1mmHg per second and about 10 mmHg per second. In someimplementations, the device further includes a controller coupled withthe pump, where the controller is configured to control a duty cycle ofthe pump. The controller may be configured to increase the duty cycle ofthe pump from a first duty cycle to a second duty cycle at a firstselected rate. The first duty cycle may be less than 100% duty cycle andthe second duty cycle may be 100% duty cycle, the first selected ratebeing between about 0.1% and about 20% increase in duty cycle persecond. The controller may be configured to increase the duty cycle ofthe pump from the second duty cycle to a third duty cycle at a secondselected rate. In some implementations, the controller is configured todynamically change the duty cycle of the pump based at least in part onthe pressure data of the pressurizable volume. In some implementations,the device further includes a controller coupled to the pump, where thecontroller is configured to control a peak-to-peak voltage (V_(pp)) ofthe pump. The controller may be configured to increase the peak-to-peakvoltage of the pump from a first peak-to-peak voltage to a secondpeak-to-peak voltage at a selected rate. In some implementations, adrive frequency of the pump is equal to or greater than about 23 kHz.

Another aspect of the disclosure relates to a method of controlling aninflation rate of an inflatable bladder. The method includes causing theinflatable bladder to inflate using a pump and contact a user'sappendage, and increasing a duty cycle of the pump from a first dutycycle to a second duty cycle at a first selected rate.

In some implementations, the first duty cycle is less than 100% dutycycle and the second duty cycle is 100% duty cycle, the first selectedrate being between about 0.1% and about 20% increase in duty cycle persecond. In some implementations, the method further includes obtainingpressure data indicative of a pressure within a pressurizable volume ofthe inflatable bladder as a function of time, and increasing the dutycycle of the pump from the second duty cycle to a third duty cycle at asecond selected rate, where increasing the duty cycle from the secondduty cycle to the third duty cycle occurs when the pressure within thepressurizable volume reaches a threshold pressure. In someimplementations, the method further includes obtaining pressure dataindicative of pressure within a pressurizable volume of the inflatablebladder as a function of time, and dynamically changing the duty cycleof the pump based at least in part on the pressure data of thepressurizable volume.

Another aspect of the disclosure relates to a device for estimating auser's blood pressure. The device includes an inflatable bladderdefining, at least in part, a pressurizable volume, a pump in fluidiccommunication with the inflatable bladder and configured to pressurizethe pressurizable volume and cause the inflatable bladder to inflate andcontact a user's appendage when the pump is activated, a pressure sensorin fluidic communication with the inflatable bladder and configured toproduce pressure data indicative of pressure within the pressurizablevolume as a function of time, where the pressure data includesoscillometric data in a first pressure profile and pulse information ina second pressure profile, and a controller coupled to the pump. Thecontroller is configured to cause the pump to pressurize thepressurizable volume to a first pressure greater than a maximumamplitude pressure of the oscillometric data in the first pressureprofile.

In some implementations, the inflatable bladder is an inflatable elasticbladder disposed about an inward-facing surface of a hole in the device,wherein the pump is configured to pressurize the pressurizable volumewhen a user's finger is positioned in the hole of the device. In someimplementations, the first pressure profile is indicative of thepressure within the pressurizable volume up to the first pressure as afunction of time, and the second pressure profile is indicative of thepressure within the pressurizable volume as a function of time afterreaching the first pressure. In some implementations, the controller isfurther configured to cause the pump to deflate the inflatable bladderso that a pressure within the pressurizable volume reaches a targetpressure less than the first pressure after reaching the first pressure.The controller may be configured to cause the pump to inflate theinflatable bladder so that a pressure within the pressurizable volumereaches a second pressure in the second pressure profile from the targetpressure, where the second pressure is based at least in part oninformation from the oscillometric data in the first pressure profile.In some implementations, the controller may be configured to maintainthe pressurizable volume at the second pressure for a durationsufficient to produce the pulse information in the second pressureprofile. The duration for maintaining the pressurizable volume at thesecond pressure may be between about 1 second and about 15 seconds. Insome implementations, the controller is further configured to maintainthe pressurizable volume at the target pressure for a durationsufficient to obtain the pulse information in the second pressureprofile, wherein the target pressure is based at least in part oninformation from the oscillometric data in the first pressure profile.In some implementations, the controller is further configured to analyzethe pulse information in the second pressure profile to determine one ormore of pulse wave analysis (PWA) features, arterial compliance,respiration, and atrial fibrillation.

Another aspect of the disclosure relates to a method of estimating auser's blood pressure. The method includes causing inflation of aninflatable bladder using a pump to contact a user's appendage, obtainingpressure data indicative of pressure within a pressurizable volume ofthe inflatable bladder as a function of time, where the pressure dataincludes oscillometric data in a first pressure profile, sustaininginflation of the inflatable bladder so that a pressure in thepressurizable volume reaches a first pressure greater than a maximumamplitude pressure of the oscillometric data in the first pressureprofile, and causing deflation of the inflatable bladder so that thepressure in the pressurizable volume reaches a target pressure from thefirst pressure. The target pressure is based at least in part oninformation from the oscillometric data in the first pressure profile.

In some implementations, the method further includes maintaining thepressurizable volume at the target pressure for a duration between about1 second and about 15 seconds. The pressure data may further includepulse information in a second pressure profile, where the pulseinformation is obtained when the pressurizable volume is maintained atthe target pressure.

Another aspect of the disclosure relates to a method of estimating auser's blood pressure. The method includes causing inflation of aninflatable bladder using a pump to contact a user's appendage, obtainingpressure data indicative of pressure within a pressurizable volume ofthe inflatable bladder as a function of time, where the pressure dataincludes oscillometric data in a first pressure profile, sustaininginflation of the inflatable bladder so that a pressure in thepressurizable volume reaches a first pressure greater than a maximumamplitude pressure of the oscillometric data in the first pressureprofile, causing deflation of the inflatable bladder from the firstpressure, and causing inflation of the inflatable bladder so that thepressure of the pressurizable volume reaches a second pressure. Thesecond pressure is based at least in part on information from theoscillometric data in the first pressure profile.

In some implementations, the method further includes maintaining thepressurizable volume at the second pressure for a duration between about1 second and about 15 seconds. The pressure data may further includepulse information in a second pressure profile, where the pulseinformation is obtained when the pressurizable volume is maintained atthe second pressure.

Another aspect of the disclosure relates to a device for estimating auser's blood pressure. The device includes an inflatable bladderdefining, at least in part, a pressurizable volume, a pump in fluidiccommunication with the inflatable bladder and configured to pressurizethe pressurizable volume and cause the inflatable bladder to inflate andcontact a user's appendage when the pump is activated, a pressure sensorin fluidic communication with the inflatable bladder and configured toproduce pressure data indicative of pressure within the pressurizablevolume as a function of time, and one or more accelerometers. The one ormore accelerometers are configured to determine relative positioning ofthe device with respect to a user's heart.

In some implementations, the inflatable bladder is an inflatable elasticbladder disposed about an inward-facing surface of a hole in the device,wherein the pump is configured to pressurize the pressurizable volumewhen a user's finger is positioned in the hole of the device. In someimplementations, the one or more accelerometers are further configuredto determine whether the device is in motion or stationary. The devicemay further include a controller configured to initiate inflation of theinflatable bladder using the pump when the one or more accelerometersdetermine that the device is positioned within a threshold elevationwith respect to the user's heart and is stationary for a thresholdduration. The controller may be further configured to turn off thedevice or enter a power-saving mode when the one or more accelerometersdetermine that the device is not positioned within the thresholdelevation with respect to the user's heart and is stationary for asufficient duration. In some implementations, the one or moreaccelerometers are configured to determine relative positioning of thedevice with respect to a user's heart by measuring an inclination aboutan axis that is orthogonal or substantially orthogonal to a verticalaxis, the inclination including a roll angle and a pitch angle, whereineach of the roll angle and the pitch angle is between about 0 degreesand about 30 degrees when the device is determined to be atapproximately the same elevation as the user's heart. In someimplementations, the device further includes one or more auscultationsensors configured to acoustically determine a location of the user'sheart. In some implementations, the device further includes one or moreoptical sensors for determining that the user's finger is positionedwithin a hole of the device, where the inflatable bladder is disposedabout an inward-facing surface of the hole of the device. In someimplementations, the device further includes one or more feedbackdevices configured to communicate to a user a positioning of the devicerelative to the user's heart, wherein the one or more feedback devicesinclude at least one of a speaker for audio feedback, a light-emittingdiode (LED) for optical feedback, a display for visual feedback, and amotor for haptic feedback.

Another aspect of the disclosure relates to a device for estimating auser's blood pressure. The device includes an inflatable bladderdefining, at least in part, a pressurizable volume, a pump in fluidiccommunication with the inflatable bladder and configured to pressurizethe pressurizable volume and cause the inflatable bladder to inflate andcontact a user's appendage when the pump is activated, a pressure sensorin fluidic communication with the inflatable bladder and configured toproduce pressure data indicative of pressure within the pressurizablevolume as a function of time, and one or more proximity sensors. The oneor more proximity sensors are configured to determine that the device ispositioned proximate to a user's heart.

In some implementations, the inflatable bladder is an inflatable elasticbladder disposed about an inward-facing surface of a hole in the device,wherein the pump is configured to pressurize the pressurizable volumewhen a user's finger is positioned in the hole of the device. In someimplementations, the one or more proximity sensors include one or bothof an auscultation sensor and a microphone configured to acousticallydetermine proximity of the user's heart. In some implementations, thedevice further includes one or more accelerometers configured todetermine whether the device is in motion or stationary. The device mayfurther include a controller configured to initiate inflation of theinflatable bladder using the pump when the one or more proximity sensorsdetermine that the device is positioned proximate to the user's heartand the one or more accelerometers determine that the device isstationary for a threshold duration.

These are other implementations are described in further detail withreference to the Figures and the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an example finger blood pressure cuffaccording to some implementations.

FIG. 2 shows a perspective view of various components of an examplefinger blood pressure cuff according to some implementations.

FIG. 3A shows a side view of an example finger blood pressure cuffaccording to some implementations.

FIG. 3B shows a cross-sectional perspective view of the finger bloodpressure cuff of FIG. 3A cut along lines A-A.

FIG. 3C shows a cross-sectional perspective view of the finger bloodpressure cuff of FIG. 3A cut along lines B-B.

FIG. 3D shows a cross-sectional side view of the finger blood pressurecuff of FIG. 3A cut along lines A-A.

FIG. 3E shows a cross-sectional side view of the finger blood pressurecuff of FIG. 3A cut along lines B-B.

FIG. 3F shows a front view of the finger blood pressure cuff of FIG. 3A.

FIG. 3G shows a cross-sectional view of the finger blood pressure cuffthrough the section plane indicated in FIG. 3F.

FIG. 4A shows an example inflatable elastic bladder according to someimplementations; front, side section, and isometric views, from left toright, are depicted.

FIG. 4B shows an example inflatable elastic bladder according to someother implementations; front, side section, isometric, side, and frontsection views, from left to right, are depicted.

FIG. 5A shows an example inflatable elastic bladder with threeinflatable lobes according to some implementations; front, side section,and isometric views, from left to right, are depicted.

FIG. 5B shows an example inflatable elastic bladder with threeinflatable twisted lobes according to some implementations; front, sidesection, isometric, and side views, from left to right, are depicted, aswell as multiple front section views along the right side of the Figure.

FIG. 5C shows an example inflatable elastic bladder with pre-inflatedlobes according to some implementations; front, side section, andisometric views, from left to right, are depicted.

FIGS. 6A and 6B show graphs of inflation profiles for a pre-inflatedelastic bladder and for an elastic bladder that is not pre-inflated.

FIG. 7 shows a graph of a typical waveform for a piezoelectric pump.

FIG. 8 shows a diagram of voltage as a function of time with a graduallychanging duty cycle of the square waveform signal driving apiezoelectric pump.

FIG. 9 shows an inflation profile of a finger blood pressure cuff usinga piezoelectric pump.

FIG. 10 shows a graph for a blood pressure measurement depicting a firstpressure profile followed by a second pressure profile, where the secondpressure profile inflates to a targeted pressure and is held at thetargeted pressure.

FIG. 11 shows a graph for a blood pressure measurement depicting a firstpressure profile followed by a second pressure profile, where the secondpressure profile deflates to a targeted pressure and is held at thetargeted pressure.

FIGS. 12 and 13 show photographs of an example finger blood pressurecuff as it may be worn during a measurement with a user placing theirhand on their chest at an angle.

FIGS. 14 and 15 show photographs of an example finger blood pressurecuff resting on a surface and with a finger inserted through an openingof the finger blood pressure cuff to take a blood pressure measurement.

DETAILED DESCRIPTION

In contrast to traditional blood pressure cuffs placed around a user'sarm or a user's wrist, the present disclosure relates to a bloodpressure cuff placed around a user's finger. A finger blood pressurecuff may offer advantages over traditional wrist or arm blood pressurecuffs because it may be less bulky, easier to use, more portable, morecompact, less obtrusive, and more comfortable to the user. However,measuring blood pressure at a user's finger is typically not regarded asaccurate and reliable because of its further distance from the user'sheart as compared with upper arm and wrist-located measurements. As usedherein, a finger blood pressure cuff refers to any system, device, orapparatus that wraps around a user's finger and is configured toestimate a blood pressure of the user.

In an embodiment, a finger blood pressure cuff may include a rigidring-shaped structure and an inflatable elastic bladder configured toinflate inwards towards a center of the ring-shaped structure andcontact a user's finger that has been inserted through the ring-shapedstructure. The elastic bladder may be inflated to pressurize it andsqueeze the user's finger and temporarily occlude blood flow in theuser's finger. Some examples of the finger blood pressure cuff mayinclude one or more sensors for detecting that the user's finger isproximate to the user's chest. The finger blood pressure cuff may,during use, generate pressure data corresponding to an applied pressureon the user's finger; such data may then be analyzed, either by thefinger blood pressure cuff or another device that receives data from thecuff, in order to obtain measurements of blood pressure and othercardiovascular data, e.g., heart rate.

Example Structure of the Finger Blood Pressure Cuff

FIG. 1 shows a perspective view of an example finger blood pressure cuff100 according to some implementations. The finger blood pressure cuff100 may include a housing 102 with an opening or hole 104 through whicha user's finger can be inserted. A generally rigid ring-shaped structureand an inflatable elastic bladder 110 may be disposed within the opening104 of the housing 102. The housing 102 may enclose one or morecomponents associated with performing the operations of the finger bloodpressure cuff 100, such as one or more of a controller or control unit,a pressure sensor, one or more inertial measurement units (e.g.,multi-axis accelerometers, gyroscopes, etc.), a piezoelectric pump (or adifferent kind of pump), a battery or other power source, and othercircuitry. The housing 102 may be supported on a base 106, where thebase 106 is connected to a power cable 108. Alternatively, the housing102 may simply have a connector port for connecting to a power cabledirectly.

FIG. 2 shows a perspective view of various components of an examplefinger blood pressure cuff 100 according to some implementations. Thefinger blood pressure cuff 100 includes a housing 102 with an opening104 for accommodating a ring-shaped structure 112 and an inflatableelastic bladder 110 within the opening 104 so that the inflatableelastic bladder 110 is disposed about an inward-facing surface of thehole or opening 104 (thus, the inflatable elastic bladder 110 appears toprovide the interior surface of the hole or opening 104 when viewed by auser). The ring-shaped structure 112 may include a hard, rigid, orsemi-rigid outer ring circumferentially disposed around the inflatableelastic bladder 110. The ring-shaped structure 112 may have a size basedon a user's finger size. The inflatable elastic bladder 110 may, incertain implementations, include a continuous, inflatable, generallyannular volume 114. Or, the inflatable elastic bladder may, in certainimplementations, include two or more inflatable volumes 112 about acenter of the opening 104 (which may be compartmentalized or mayalternatively, as in the depicted example, define a contiguous interiorbladder volume). The two or more inflatable volumes 112 may be two ormore inflatable lobes symmetrically distributed about the center of theopening. However, it will be understood that in some implementations,the two or more inflatable lobes may be non-symmetrically distributedabout the center of the opening. In some implementations, the inflatableelastic bladder 110 may comprise three inflatable lobes. Upon inflation,e.g., when the pump is used to pressurize the pressurizable volume, theinflatable elastic bladder 110 may expand inwards towards the center ofthe hole or opening 104 and press against a user's finger that isinserted in the opening 104 and provide sufficient arterial clamping toat least temporarily occlude blood flow in the user's finger.

As noted above, the ring-shaped structure 120 and the inflatable elasticbladder 110 may, in combination, define a pressurizable volume that maybe pressurized in order to cause the inflatable elastic bladder 110 toexpand in towards the center of the ring-shaped structure 120. In manyimplementations, the ring-shaped structure 120 and the inflatableelastic bladder 110 may be generally radially or axially symmetric (withrespect to the ring-shaped structure 120, it is to be understood thatsuch general radial or axial symmetry may apply to the “interior-facing”surfaces, e.g., those surfaces that face towards the interior of thering shape, and that the remainder of the ring-shaped structure mayexhibit a lack of symmetry and be other than ring-shaped), with thecenter axes of both components generally aligned and with thering-shaped structure 120 encircling the inflatable elastic bladder 110.Put another way, the ring-shaped structure 120 may provide a rigidframework that supports or helps support the inflatable elastic bladder110 and may also provide a ring-shaped, rigid surface that defines partof the pressurizable volume of the bladder 110, with the majority of theremainder of the pressurizable volume of the bladder 110 being providedby the inflatable elastic bladder 110.

Several components may be enclosed within the housing 102 of the fingerblood pressure cuff 100. As shown in FIG. 2, the finger blood pressurecuff 100 may include a pump 130 such as a piezoelectric pump that isfluidically connected with the pressurizable volume (which may also bereferred to as a “bladder volume” or the like) of the inflatable elasticbladder 110 so that the pump 130 can pressurize the pressurizable volumeand inflate the inflatable elastic bladder 110. The pump 130 may befluidically connected with the inflatable elastic bladder 110 via a pumpinlet/outlet 132 in the housing 102 and via one or more ports 122 in thering-shaped structure 120. The ports 122 may be holes or openings in thering-shaped structure 120, where the holes or openings may be positionedin an annular passage 124 of the ring-shaped structure 120. While twoalternative inflatable elastic bladders 110 are shown in FIG. 2—only onewould be used in a particular finger blood pressure cuff 100, thoughboth are shown in this example figure. The various inflatable elasticbladders 110 may be interchangeable and thereby capable of beinginstalled in, and removed from, the housing 102. The finger bloodpressure cuff 100 may further include a pressure sensor 140 that is alsofluidically connected with the pressurizable volume of the inflatableelastic bladder 110 to allow measurement of the pressure within thepressurizable volume over time. The finger blood pressure cuff 100 mayfurther include a controller or control unit that is configured tocontrol the pump 130 and to receive and process data from the pressuresensor 140, where the controller or control unit along with othercircuitry may be mounted on one or more printed circuit boards (PCBs)150. The finger blood pressure cuff 100 may further include a battery152 for powering the finger blood pressure cuff 100. As shown in FIG. 2,a charger may be configured to recharge the battery 152, e.g., viainductive charging or other charging technique, and may be incorporatedinto a base 106 on which the blood pressure cuff 100 may be placed. Theblood pressure cuff 100 may also include one or more communicationinterfaces, e.g., USB, Bluetooth, etc., that may be used to send data,either directly or by way of one or more intermediary devices, from thedevice to another device, e.g., a smartphone, computer, or remoteserver. The data may be processed using the processor or processorswithin the housing 102, processors or a processor in another device,e.g., a server or smartphone, or a combination of such options.

FIG. 3A shows a side view of an example finger blood pressure cuff. FIG.3B shows a cross-sectional perspective view of the finger blood pressurecuff of FIG. 3A cut along lines A-A. FIG. 3C shows a cross-sectionalperspective view of the finger blood pressure cuff of FIG. 3A cut alonglines B-B. FIG. 3D shows a cross-sectional side view of the finger bloodpressure cuff of FIG. 3A cut along lines A-A. FIG. 3E shows across-sectional side view of the finger blood pressure cuff of FIG. 3Acut along lines B-B.

In FIGS. 3B-3E, an opening 104 of a housing 102 of the finger bloodpressure cuff 100 accommodates an inflatable elastic bladder 110. Theinflatable elastic bladder 110 occupies a volume within the opening 104.In some implementations, the inflatable elastic bladder 110 may have agenerally triangular shape along a portion of its length to provide athree-lobed design. As shown in FIGS. 3B-3E, the inflatable elasticbladder 110 includes three lobes that are each configured to expandtowards a center of the opening 104 upon inflation. The use of two ormore lobes provides a centering effect on the finger and encourages thefinger to move towards the center of the opening 104, thereby promotingeven inflation of the lobes, and more radially uniform application ofpressure on the finger by the bladder 110. Moreover, the use of two ormore lobes reduces inaccuracies that may result from a user's fingerbeing small relative to the inflatable elastic bladder 110. Withoutmultiple lobes, a bladder will stretch and a tensile strength of thebladder 110 supports some of the internal pressure, thereby reducingpressure on the finger. This effect is more significant with smallerfingers and is minimized with the application of multiple lobes.

Inflation air may be provided from a pump 130 (e.g., piezoelectric pump)through a plurality of holes or ports 122 in the ring-shaped structure120 to inflate the inflatable lobes of the elastic bladder 110. Itshould be understood that alternative designs may utilize a liquid,e.g., water or oil, instead of air (or may use a gas other than air, ifdesired) and may utilize pumps that may be designed for use with liquidsinstead of gases—in such cases, a reservoir, e.g., another expandablebladder, may be used to store the working liquid that is not within theinflatable bladder mechanism. One or more pressure sensors 140 in thefinger blood pressure cuff 100 may be configured to measure the pressurewithin the pressurizable volume of the inflatable elastic bladder 110,which is generally proportionate to the pressure actually applied by thebladder 110 on a user's finger positioned in the opening 104.Accordingly, the pressure sensor 140 may be used to produce pressuredata indicative of the pressure within the pressurizable volume of theinflatable elastic bladder 110. The sensed pressure within thepressurizable volume is generally proportionate to the actually appliedpressure on the user's finger positioned in the opening 104. Suchpressure data may be used to provide a “pressure profile” that visuallyrepresents the pressure measured within the pressurizable volume of theinflatable elastic bladder 110 over time. As shown in FIGS. 3B and 3D, apressure sensor 140 may be contained within the housing 102 and adjacentto the ring-shaped structure 120 and the inflatable elastic bladder 110.Each of the pressure sensor(s) 140 and the pressurizing pump(s) 130 maybe electrically coupled with a controller. The controller may include atleast one of a general purpose single- or multi-chip processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, ordiscrete hardware components. In some implementations, the controllerincludes a processor, where the processor may be controlled bycomputer-executable instructions stored in memory so as to providefunctionality described herein. The processor and other circuitry may beprovided on one or more PCBs 150 enclosed in the housing 102.

In some implementations, the inflatable elastic bladder 110 may besealed or attached to the ring-shaped structure 120, where the seal orattachment may form a relatively airtight volume. While the inflatableelastic bladder 110 and ring-shaped structure 120 may form an airtightvolume, it is understood that in some implementations the inflatableelastic bladder 110 and ring-shaped structure 120 may include a leakagepoint (e.g., designed-in leak) to reduce inflation speed and/or providea controlled or “automatic” mode of deflation. In some implementations,the inflatable elastic bladder 110 may be welded or joined to thering-shaped structure 120 via a thermoplastic material or thermoplasticcoating on the inflatable elastic bladder 110. In some implementations,the inflatable elastic bladder 110 may be attached to the ring-shapedstructure 120 by an adhesive or using a suitable chemical bondingtechnique.

Typical OBPM systems use inflatable bladders made of flexible, butgenerally inelastic, materials such as vinyl. However, the finger bloodpressure cuff 100 of the present disclosure uses an inflatable bladder110 made of an elastic material. In some implementations, the elasticmaterial includes silicone or other elastomer having a Young's modulusbetween about 0.001 GPa and about 0.1 GPa or between about 0.003 GPa andabout 0.05 GPa, which are orders of magnitude lower than that ofmaterials like vinyl which are presently used in typical blood pressurecuffs. For example, the elastomer can have a Young's modulus of about0.005 GPa. In the context of a finger cuff apparatus, pressure lossusing an elastic material is smaller compared to using an inelasticmaterial. Without being limited by any theory, the elastic material mayprovide flexibility to ensure that the pressure inside of the inflatablebladder 110 is optimally transferred to the user's finger to minimizepressure loss. Moreover, an inelastic material may have more folds andcreases that allow the bladder material to fold over and press againstitself, introducing additional sources of pressure loss from thematerial itself. As used herein, pressure loss refers to the differencebetween the internal pressure of the inflatable bladder (i.e., pressureused to inflate and stretch the bladder 110) and the externally appliedpressure to the blood vessel of the user's finger. A reduced pressureloss using an elastic material may allow the finger blood pressure cuff100 to be used on a wide range of fingers of different sizes with anegligible difference in signal output.

In some implementations, the inflatable elastic bladder 110 may berelatively thin, such as between about 0.1 mm and about 0.75 mm thick orbetween about 0.25 mm and about 0.5 mm thick. Thin inflatable elasticbladders 110 may reduce pressure loss while permitting expansion of theinflatable elastic bladder 110.

In some implementations, the elastic material may be treated or coatedto reduce a tackiness of the elastic bladder. For example, the elasticmaterial may be treated by ultraviolet (UV) oxidation to reduce itstackiness or friction coefficient, thereby allowing for easier insertionof a person's finger into the opening 104. For example, subjecting asilicone-based inflatable elastic bladder to UV irradiation, corona, orplasma in combination with the introduction of polar groups into thesurface region of the silicone may cause oxidation resulting in avitrified silica-like surface layer. In other instances, the inflatableelastic bladder may be treated with a chemical coating, such as NuSil'sR-2182 low coefficient of friction silicone coating, which may, whencured, offer such low tackiness and/or friction coefficient.

In some implementations, such as that shown in FIG. 3E (the other FIGS.3A-3D, 3F, and 3G do not show this implementation), the housing 102 maybe equipped with a stretchable textile-based cover or tube 107 thatcovers the inflatable elastic bladder and keeps it from directlycontacting a person's skin during insertion and measurement. The covermay be made, for example, of a thin, stretchable woven material such asLycra™ or Spandex™ so that it may stretch to accommodate expansion ofthe inflatable elastic bladder 110 without exerting too much compressiveforce on the inflatable elastic bladder 110.

In some implementations, the elastic material of the bladder 110 may besubstantially transparent to permit light of certain wavelengths to passthrough. Thus, optical sensors may be incorporated (e.g., within theinflatable elastic bladders 110) to perform additional functions withthe finger blood pressure cuff 100. In some such implementations, aflexible printed circuit may be bonded or otherwise attached to asurface of the bladder 110 that defines, in part, the bladder volume.Such a circuit may include a photodetector and a photoemitter, forexample, that form a photoplethysmographic (PPG) sensor. Thephotoemitter may be configured to direct light through the bladder 110and into the dermis of the finger during a measurement, and thephotoemitter may then measure the amount of this light that isdiffusively reflected back out of the dermis and back through thebladder 110. The PPG sensor may otherwise operate in a manner typical ofPPG sensors. In other such implementations, a transmissive PPG sensormay be used in which a photoemitter is positioned within the bladdervolume on one side of the opening 104 and a photodetector is positionedwithin the bladder volume on another side of the opening 104 directlyacross or in a position therebetween. Even when a person's finger isinserted in the opening 104, the light that is emitted from thephotoemitter may still, if bright enough, pass through the finger or atleast a portion of the finger, thereby being modulated by the blood flowthrough the finger, and into the photodetector, where the detectedsignal may be used as an input for the PPG sensor. Such a PPG sensor maybe configured to measure heart rate, blood oxygenation, SpO2 levels, andother cardiovascular parameters.

In some implementations, the inflatable elastic bladder 110 may includefolds and other non-uniformities of varying flexibility that can serveto reduce pressure loss. For example, the inflatable elastic bladder 110may include lobes as discussed above to reduce pressure loss.

In some implementations, the inflatable elastic bladder 110 may bemolded from a single material. In other implementations, the inflatableelastic bladder 110 may be molded from more than one material.

A length (where length is measured along the axis along which the fingeris inserted into the bladder 110) of the inflatable elastic bladder 110may be sized based on a length of a user's finger. A longer inflatableelastic bladder 110 may provide improved arterial clamping. In someimplementations, a length of the inflatable elastic bladder 110 may bebetween about 0.5 inches and about 1.5 inches or between about 0.75inches and about 1.25 inches. In testing, a length of about 80% of theaverage adult phalange length was found to work well for a variety ofadult test subjects with varying finger and hand sizes and still provideadequate arterial clamping and thus good blood pressure measurements.

In some implementations, a volume of the inflatable elastic bladder 110when fully inflated may be between about 1 cubic centimeter and about 20cubic centimeters or between about 3 cubic centimeters and about 10cubic centimeters. This volume is significantly less than conventionalinflatable bladders of conventional OBPM systems.

FIG. 3F shows a front view of the finger blood pressure cuff of FIG. 3A.FIG. 3G shows a cross-sectional side view of the finger blood pressurecuff of FIG. 3F cut along lines C-C. In FIG. 3G, the inflatable elasticbladder 110 further includes a pair of bellows 116, one at each end ofthe bladder 110. As used herein, “bellows” may refer to portions of theinflatable elastic bladder 110 that wrap, bend, or fold back from aremainder of the inflatable elastic bladder 110, e.g., from the membraneof the inflatable elastic bladder 110, to allow it to expand orcontract. Here, the bellows 116 may be annularly disposed around theinflatable elastic bladder 110 and configured to reduce inflationresistance by allowing the bladder 110 to expand inwards towards thecenter of the opening 104 without requiring as much stretching of thebladder membrane. In FIG. 3F, a three-lobed bladder is shown, as well asarrows indicating how these lobes will inflate and dashed linesindicating the outlines of the lobes when in a pressurized state. Someimplementations may have more than three lobes, e.g., four lobes, fivelobes, and so forth. Some implementations may have less than threelobes, e.g., two lobes. As shown in FIG. 3G, the bellows 116 may befolded, bent, shaped, or conformed to reduce inflation resistance by theinflatable elastic bladder 110 during inflation. The bellows 116 may bedisposed in the opening 104 of the housing 102 and attached to thehousing 102 via one or more o-rings or seal beads 118 that are integralwith the bladder 110, which may be compressed between the ring-shapedstructure 120 and the housing 102 in order to clamp the bladder 110 tothe ring-shaped structure 120 and form an airtight seal of a bladdervolume or pressurizable volume 112. Thus, for example, the ring-shapedstructure 120 may be thought of as having a first end and second endwith a substantially cylindrical inner surface spanning between them(the surface may be cylindrical in overall shape but may, for example,have discontinuities, such as pressure ports, or be slightly ellipticalor may have a non-regular shape that matches the cross-section profileof an average person's finger); the inflatable elastic bladder 110 mayhave a first seal bead and a second seal bead, each of which is sizedand shaped so as to be able to be butted up against the first end andthe second end, respectively. By compressing the first and second sealbeads against the first and second ends of the ring-shaped structure120, the inflatable elastic bladder 110 may be sealed to the ring-shapedstructure 120, thereby forming the pressurizable volume or bladdervolume 112. Also visible in FIG. 3G is an annular passage 124 that isprovided between the ring-shaped structure 120 and the housing 102 andwhich provides a fluidic communication path between the holes/ports 122that lead to the bladder volume 112 and the inlet/outlet ports 132, 142for the pump 130 and/or pressure sensor 140.

In some implementations, the housing 102 may include a circumferentiallip 102′ (while the depicted implementation does not have suchpronounced circumferential lips, the dotted outlines 102′ indicate howsuch circumferential lips may appear) around the hole or opening 104 (ifthe hole is a through-hole, then the circumferential lip may optionallybe on both sides of the hole; if a blind hole, then only on one side ofthe housing where the hole is). The circumferential lip may extendaround the hole or opening 104 and may form an aperture smaller than thehole 104 (or at least, smaller than the hole or opening past where thecircumferential lip is) and the lip may obscure some or all of theinflatable elastic bladder 110 from view when the finger blood pressurecuff is viewed along the center axis of the hole or opening 104 (and atleast when the inflatable blood pressure cuff is at zero atmosphericgauge pressure). In some such implementations, the circumferential lipmay obscure the fold of the bellows 116, e.g., the region where thebellows membrane transitions to the bellows 116, from view along thecenter axis. The circumferential lip may therefore help protect theinflatable elastic bladder 110 (in particular, the bellows fold) fromabrasion or other wear and tear that may be caused by repeated insertionof a finger into the finger blood pressure cuff.

FIG. 4A shows an example inflatable elastic bladder 410 according tosome implementations. This implementation of the inflatable elasticbladder 410 is axially symmetric about an axis, e.g., the center axis ofthe hole, and features a pair of bellows 416, as discussed above. Theinflatable elastic bladder 410 includes a bladder membrane 411 fordefining a bladder volume or pressurizable volume and further includesone or more seal beads 418 integral with the bladder membrane 411 andconfigured to attach to a housing of a finger blood pressure cuff. Suchan inflatable elastic bladder 410 may be used to provide a pressurizablevolume that has a continuous annular shape.

It is to be understood that the term “center axis,” as used herein, isinclusive of axes that may not necessarily pass through the center of aparticular structure or geometry, but that may be located in closeproximity thereto (for example, if an opening is slightly asymmetric,the center axis may be a center axis that passes through a centroid ofthe opening, or it may pass through a center of a circle thatcircumscribes the opening). Generally speaking, however, the center axisof a structure or feature may be located within a first distance of a“true” center axis of the structure or feature, e.g., a center axispassing through a centroid or that forms an axis of symmetry of thatstructure or feature. The first distance may, for example, be ±10% ofthe largest dimension of the feature defining the center axis. Forexample, if the opening is generally circular but not actually circular,the center axis may pass through a point within ±10% of the largestdimension of the opening from the opening's centroid.

FIG. 4B shows another example inflatable elastic bladder 420 accordingto some other implementations. The inflatable elastic bladder 420 ofFIG. 4B is identical to that of FIG. 4A except that this bladder 420also includes a plurality, e.g., four, longitudinal ribs 421, which maybe included to provide some stiffness to the bladder 420 and potentiallyencourage folds/pleats in the bladder 420 to form at pre-determinedlocations. The longitudinal ribs 421 may extend along directionsparallel to the center axis of the hole (or the axis of axial or radialsymmetry of the inflatable elastic bladder) and may be arranged in acircular array centered on the center axis. Each of the inflatableelastic bladders 410, 420 in FIGS. 4A and 4B depict inflatable elasticbladders with an axially uniform annular inflatable volume.

FIG. 5A shows an example inflatable elastic bladder 510 with threeinflatable lobes 511 according to some implementations. It is importantto understand that the shape that is depicted in the example depicted inFIG. 5A is the shape of the example bladder 510 at rest, i.e., notsubject to pressurization (thus, for example, the shape of the bladderwhen at zero gauge pressure—the pressure within the bladder beingequalized with the ambient atmospheric pressure outside of the bladder).Thus, the as-molded shape of the bladder 510 of FIG. 5A includes thelobe features that are visible. When this bladder 510 is pressurized,the lobes 511 will expand inwards, starting with the points that arealready closest to the center, thereby applying pressure to the fingerat generally equally-spaced locations around the circumference of thefinger.

FIG. 5B shows an example inflatable elastic bladder 520 with threehelically twisted lobes 521 according to some implementations. Thehelical twist in the lobes 521 may be included to cause creases to formbetween the lobes 521 to follow helical paths instead of paths that aregenerally aligned with the finger bones/center axis of the bladder 520.As can be seen in cross-sections J-J through M-M, the triangular openingin the middle of the membrane experiences a helical twist through about40° (as shown by the dash-dot-dash reference axis in those Figures)along the length of the bladder 520. This reduces the chance that largerarteries in the finger, which generally extend in directions alignedwith the finger bones, may align with one of the creases and thereforenot be subjected to as much clamping pressure as the regions of thefinger that are in contact with the middles of the lobes 521.

FIG. 5C shows an example inflatable elastic bladder 530 with centeringlobes 531 that extend further towards the center of the opening ascompared with the tri-lobe design of FIG. 5A so that a finger that isinserted will be more aggressively “centered” by the lobes 531 accordingto some implementations.

Each of FIGS. 5A-5C show a perspective view, a front view, and across-sectional view based on a cutaway of the front view. FIG. 5Bfurther shows a side view of the inflatable elastic bladder 520 withhelically twisted lobes 521, with multiple cross-sectional views cutfrom along lines J-J, K-K, L-L, and M-M for depicting the twisted lobes521.

In some implementations, introducing multiple lobes 511 in theinflatable elastic bladder 510 as shown in FIG. 5A may improveconformance of the inflatable elastic bladder 510 on various fingersizes. In some implementations, introducing twisted lobes 521 in aninflatable elastic bladder 520 as shown in FIG. 5B may improve arterialclamping and further reduce pressure loss. In some implementations,using centering lobes 531 in the inflatable elastic bladder 530 as shownin FIG. 5C, or pre-inflating the lobes so that they appear similar tothose in FIG. 5A, may provide benefits, such as improved contact with auser's finger during insertion, and thus further reduce pressure loss.

Typical OBPM systems do not inflate an inflatable bladder until a bloodpressure measurement is initiated. However, the finger blood pressurecuff of the present disclosure may include a pre-inflation mechanism,e.g., maintaining a slight amount of pressurization in the bladdersufficient to distend the bladder into a configuration similar to theelastic bladder as shown in FIG. 5C prior to further inflating theelastic bladder for a blood pressure measurement. The elastic bladdermay occupy a desired volume, e.g., a partially inflated volume such asshown in FIG. 3F, in the opening prior to initiation of a blood pressuremeasurement. A pre-inflated elastic bladder may reduce pressure lossthat may result from inflating the elastic bladder to a certain volumeto gain contact with a user's finger. A pre-inflated elastic bladder maycontact or nearly contact a user's finger positioned in the openingregardless of whether the user's finger is small or large. Pre-inflationreduces the volume requirement of inflating the elastic bladder toobtain contact with the user's finger. Whereas conventional OBPM systemsmay require wrapping and cinching an inflatable bladder around a user'sappendage to obtain “tight” or “snug” contact, a pre-inflated elasticbladder introduces volume in the bladder to obtain contact withoutchanging the diameter of the opening or outer diameter of the bladder.

In some implementations, the finger blood pressure cuffs of the presentdisclosure may include a controller that is configured to control thepump to pre-inflate the inflatable elastic bladder from a firstpressure, e.g., atmospheric pressure, to a second pre-measurementpressure or second pressure, as discussed above, prior to insertion of afinger. Upon insertion of a finger, the controller may cause the pump tofurther inflate the inflatable elastic bladder to a third pressure atwhich the pressure sensor detects pulsatile variations in the pressure,e.g., pulsatile variations in line with those caused by heartbeats (forexample, those with a periodicity of between about 50 cycles per minuteand 200 cycles per minute) and then to a fourth pressure at which thepulsatile variations in the pressure decrease to a first predeterminedlevel, e.g., 0 or less than 5% of the maximum pulsatile variationsobserved. Alternatively, the controller may cause the pump to pressurizethe inflatable elastic bladder to the fourth pressure after reaching thesecond pressure, e.g., by pressurizing the inflatable elastic bladder toa pressure that is higher than the maximum expected measurement pressureand then allowing the pressure to decrease in a controlled manner untilpulsatile variations in the pressure signal are detectable. In suchimplementations, the pressure may then be allowed to further decrease ina controlled manner to reach the third pressure.

FIGS. 6A and 6B compare inflation profiles (pressure profile duringinflation) between pre-inflated bladders and non-pre-inflated bladders.FIG. 6A depicts inflation profiles for pre-inflated bladders and FIG. 6Bdepicts inflation profiles for non-pre-inflated bladders. Each of FIGS.6A and 6B depict inflation profiles for (1) a pressure sensed by thepressure sensor (depicted by pressure 601, 611), (2) an actual appliedpressure on a medium-sized finger (depicted by pressure 602, 612), and(3) an actual applied pressure on a small-sized finger (depicted bypressure 603, 613). The pressures where one or more pulses are recordedare used to estimate blood pressure. The one or more pulses in theinflation profile may be part of oscillometric data for estimating auser's blood pressure. In FIG. 6A for pre-inflated bladders, at a giventime when the one or more pulses are recorded, a first pressuredifference between the observed pressure 601 and the actual appliedpressure 602 on a medium-sized finger is represented by ΔP₁, and asecond pressure difference between the observed pressure 601 and theactual applied pressure 603 on a small-sized finger is represented byΔP₂. In FIG. 6B for non-pre-inflated bladders, at a given time when theone or more pulses are recorded, a third pressure difference between theobserved pressure 611 and the actual applied pressure 612 on amedium-sized finger is represented by ΔP₃, and a fourth pressuredifference between the observed pressure 611 and the actual appliedpressure 613 on a small-sized finger is represented by ΔP₄. FIGS. 6A and6B show that with pre-inflated bladders, the actual applied pressure602, 603 is closer to the observed pressure 601 and varies less withdifferent finger sizes. Therefore, the final estimation of bloodpressure will generally be more accurate. With non-pre-inflatedbladders, the actual applied pressure 612, 613 is significantly lessthan the observed pressure 611 and is even more significant for smallerfinger sizes.

Pump Control of the Blood Pressure Cuff

A pressurizing pump may be used to control inflation/deflation of aninflatable bladder of a blood pressure cuff. The pressurizing pump maybe fluidically connected to the pressurizable volume of inflatablebladder, where the pressurizing pump is configured to pressurize thepressurizable volume and cause the inflatable bladder to inflate andcontact a user's appendage (e.g., a user's finger) when the pressurizingpump is activated. When the pump is activated, the pressurizable volumeis inflated and expands towards the user's appendage to contact theuser's appendage under the driving of the pressurizing pump. A bloodpressure measurement may occur when a user's appendage is inserted in anopening of the blood pressure cuff and the pump is activated topressurize the pressurizable volume and contact the user's appendage.The blood pressure cuff may include a pressure sensor for generatingpressure data indicative of pressure in the pressurizable volume as afunction of time, where the pressure data can be used to obtain bloodpressure measurements of the user.

In some implementations, the pressurizing pump may be a piezoelectricpump. Typical piezoelectric pumps for controlling inflation maypressurize an elastic bladder too quickly for detecting a pulse wave ina blood pressure measurement. For example, a typical pump may pressurizethe elastic bladder at an inflation rate of greater than 20 mmHg persecond, greater than 50 mmHg per second, greater than 80 mmHg persecond, or greater than 100 mmHg per second. Such high inflation ratesare too fast for pressurizing a volume around a user's finger. Then, apulse wave in a blood pressure measurement is not detected. However, theblood pressure cuff of the present disclosure includes a pump andcontrol hardware that controls the inflation rate to allow for detectionof a pulse wave in a blood pressure measurement. In someimplementations, the inflation rate (or, more accurately, thepressurization rate) of the pump is less than about 20 mmHg per second,less than about 10 mmHg per second, or less than about 5 mmHg persecond. For example, the inflation rate of the pump can be controlled tobe between about 1 mmHg and about 10 mmHg per second. Furthermore, theinflation rate of the pump may be modulated to maintain a linear ornear-linear pressure-time history for the bladder pressure, excludingany non-linearities from the oscillometric waveform. For example, thepressure rise in the bladder can be maintained to be approximatelylinear at an inflation rate between about 1 mmHg per second and about 10mmHg per second, such as about 4 mmHg per second.

The blood pressure cuff of the present disclosure may include acontroller or control unit coupled with the pump. The control unit orcontroller may include at least one of a general purpose single- ormulti-chip processor, a digital signal processor, an applicationspecific integrated circuit, a field programmable gate array or otherprogrammable logic device, discrete gate or transistor logic, ordiscrete hardware components. In some embodiments, the controller may becapable of controlling the pump according to instructions (e.g.,software) stored on one or more non-transitory computer-readable media.Such non-transitory media may include the memory of the blood pressurecuff. The controller is configured to input control signals to drive thepump according to various parameters.

Additional control hardware may be coupled with the controller forcontrolling various operations of the pump or, more generally, the bloodpressure cuff. The controller may be coupled with, for example, a DC-DCbooster circuit for varying a drive voltage of the pump. The controllermay optionally be coupled with an exhaust valve for deflating andcontracting the pressurizable volume of the inflatable bladder. Forexample, in some implementations (such as that depicted in FIG. 3E; theFIGS. 3A-3D, 3F, and 3G do not depict these additional features), avalve 105 may be fluidically connected with the pressurizable volume,e.g., via the annular passage 124. The valve 105 may, for example, be acontrollable valve operated by the controller or may be a mechanicalpop-off valve that automatically allows pressure beyond a pre-set point,e.g., 275 mmHg to 300 mmHg gauge pressure, to be bled off. In the caseof a controllable valve 105, the controller may monitor the data fromthe pressure sensor may cause the valve 105 to release pressure thatexceeds a preset threshold, e.g., 275 mmHg to 300 mmHg gauge pressure.In some implementations, the housing 102 may also or alternativelyinclude a mechanical plug 103 that may be accessible by a user from theexterior of the device; the mechanical plug 103 may be configured to beeasily removable by a user in the event that the pressure within theinflatable elastic bladder 110 exceeds a comfortable amount (and/or ifthere is a malfunction that prevents the pump from turning off, forexample).

The blood pressure cuff of the present disclosure includes thecontroller for varying one or more parameters to influence the inflationrate of the pump. The parameters for controlling the inflation rate maybe fixed during a blood pressure measurement or may be continuouslyvaried during the blood pressure measurement. By way of an example, arate of change of a duty cycle may be fixed during a blood pressuremeasurement, e.g., set according to a preset sequence of duty cyclelengths, or the rate of change of a duty cycle may dynamically changebased at least in part on pressure readings from the blood pressuremeasurement, e.g., the duty cycle length may be varied based on feedbackfrom a pressure sensor.

The controller may be configured to control at least one of a dutycycle, voltage, or drive frequency of the pump. Controlling one or moreof the aforementioned characteristics of the pump may control aninflation rate of the pump.

A piezoelectric pump generally discharges air at a flow rate when inresponse to alternating drive signals when an AC current is applied.Typical piezoelectric pumps are engineered to operate a response toalternating driving signals of a particular frequency and voltage, e.g.,a square wave signal having a nominally constant frequency and voltage.It will be understood that a sine wave signal may be applied, a squarewave signal may be applied, and so on. As shown in FIG. 7, a typicalpiezoelectric pump may be operated using a square waveform signal thoughit will be understood that other piezoelectric pumps may be operatedusing a sine wave signal or other alternating driving signal. Thealternative driving signal may be characterized by an amplitude V₀ and adrive frequency f₀. An inflation rate of the pump may be determined atleast in part by controlling characteristics such as the amplitude anddrive frequency of the pump. A peak-to-peak voltage V_(pp) may be usedwhen discussing the value of the voltage applied to the pump, where theamplitude V₀ is half the value of the peak-to-peak voltage V_(pp). Adrive frequency of the signal can be, for example, 23 kHz, and a drivingvoltage can be, for example, 5-30 V_(pp).

Though the drive frequency cannot generally be adjusted, there may besome ability to adjust within the design limits of the driving signal.Accordingly, in some implementations, the drive frequency of the pumpmay be adjusted to control the pump speed, thereby controlling itsinflation rate. However, dropping the drive frequency below theengineered lower limit of acceptable driving signal frequencies maycause the pump to no longer operate correctly, and it may be unable toadequately provide any pressurization. Nonetheless, in some embodiments,the controller coupled to the pump may be configured to modify the drivefrequency to change the inflation rate of the pump. In some embodiments,the drive frequency of the pump is equal to or greater than about 23kHz. The drive frequency of the pump may be modified to be outsideaudible noise.

In addition or in the alternative, the inflation rate of thepiezoelectric pump can be controlled by controlling the voltage of thepump. Also referred to as “amplitude modulation,” the voltage applied tothe pump may be controlled within a given desired amplitude range. Insome embodiments, the voltage applied to the pump may increase withinthe desired amplitude range. If the peak-to-peak potential differenceV_(pp) goes from about 12 V_(pp) to about 40 V_(pp), then the amplituderange is from about 6 V to about 20 V. A higher voltage or amplitudegenerally corresponds to a larger volume displacement with apiezoelectric pump. In some embodiments, the controller may beconfigured to increase the peak-to-peak voltage of the pump from a firstpeak-to-peak voltage to a second peak-to-peak voltage at a selectedrate. By way of an example, the first peak-to-peak voltage may bebetween about 5 V_(pp) and about 20 V_(pp) (e.g., 10 V_(pp)) and thesecond peak-to-peak voltage may be between about 40 V_(pp) and about 80V_(pp) (e.g., 60 V_(pp)), which corresponds to an amplitude range of2.5-10 V (e.g., 5 V) to 20-40 V (e.g., 30 V). The amplitude maygradually increase according to a selected rate. In some embodiments,the amplitude increases at a selected rate between about 2 V per secondand about 10 V per second, such as about 5 V per second. Changing theamplitude of the driving signal may result in a change in the amount ofnoise heard from the pump. In some implementations, amplitude modulationmay reduce noise emanating from the piezoelectric pump.

In addition or in the alternative, the inflation rate of the pump may becontrolled by controlling the duty cycle of the pump. A duty cycle canrefer to the percentage of on time (T_(on)) during the total of on timeand off time, where T=T_(on)+T_(off) in a given cycle. The duty cyclecan gradually increase at a selected rate to reach a desired duty cycle.In some implementations, the selected rate may be fixed during a bloodpressure measurement, and a duty cycle may increase from a first dutycycle (e.g., less than 100% duty cycle) to a second duty cycle (e.g.,100% duty cycle) at a selected rate. In some implementations, a selectedrate may be between about 0.1% and about 20% increase in duty cycle persecond. By way of an example, the duty cycle may increase from 40% dutycycle to 100% duty cycle at a rate of about 1% increase in duty cycleper second.

In some implementations, the selected rate may dynamically change duringa blood pressure measurement, and a duty cycle may increase from a firstduty cycle (e.g., less than 100% duty cycle) to a second duty cycle(e.g., greater than the first duty cycle) at a first rate, and a dutycycle may increase from the second duty cycle to a third duty cycle(e.g., greater than the second duty cycle) at a second rate. The firstrate is different than the second rate, where each of the first andsecond rates is between about 0.1% and about 20% increase in duty cycleper second. By way of an example, the duty cycle may increase from 20%duty cycle to 30% duty cycle at a rate of about 1% increase in dutycycle per second, and the duty cycle may subsequently increase from 30%duty cycle to 50% duty cycle at a rate of about 5% increase in dutycycle per second. The duty cycle may increase until 100% duty cycle isreached or, in some cases, until a lower level of duty cycle is reached.

FIG. 8 shows a diagram of voltage as a function of time with a graduallychanging duty cycle of the square waveform signal driving apiezoelectric pump. To be clear, the duty cycle signal is used tomodulate the fixed-frequency driving signal for the pump; when the dutycycle signal is 100%, the fixed-frequency driving signal is provided tothe pump. When the duty cycle signal is 0%, the fixed-frequency drivingsignal is not provided to the pump. Thus, the pump is driven at aconstant frequency during the intervals of the duty cycle where the dutycycle phase is “on”, and during the duty cycle “off” phase the pump isnot driven In FIG. 8, the piezoelectric pump is being driven by a dutycycle signal with a pulse wave frequency of about 5000 Hz. As shown inFIG. 8, the duty cycle gradually increases from 70% duty cycle to 100%duty cycle at a rate of 10% increase in duty cycle per second. Whereasthe square waveform signal in FIG. 7 is continuous, the square waveformsignal in FIG. 8 is discontinuous or “chopped up.” This causes, as notedabove, the piezoelectric pump to operate intermittently and inflate thebladder at a slower inflation rate instead of at full speed. Such aslower inflation rate may be suitable for inflating smaller volumes.

As discussed below, the controller may be further coupled with apressure sensor in fluidic communication with the inflatable bladder andconfigured to produce pressure data indicative of pressure within thepressurizable volume as a function of time. In some implementations, thecontroller is configured to change the increase in the duty cycle fromthe first rate to the second rate when a pressure within thepressurizable volume reaches a threshold pressure. This allows theincrease in the duty cycle to slow down or speed up when certainpressure levels are reached, thereby controlling the inflation rate ofthe pump. For example, the first rate may be 1% increase per second andthe second rate may be 0.5% increase per second, or vice versa. In someimplementations, the threshold pressure may be a pressure between about50 mmHg and about 250 mmHg, or between about 100 mmHg and about 180mmHg. In some implementations, the controller is configured todynamically change the duty cycle of the pump based at least in part onthe pressure data of the pressurizable volume. Certain duty cycles maynot be powerful enough to pressurize the pressurizable volume pastcertain pressure levels, and so duty cycles may be dynamically tunedbased on the pressure data.

Modifying the duty cycle of the pump may cause the distortions in thelinearity of the inflation profile, which may interfere with accuratereading and recording of pulse information in a blood pressuremeasurement. Accordingly, controlling the duty cycle and the selectedrate of change of the duty cycle may be optimized to achieve a linear orsubstantially linear inflation profile. In other words, the duty cyclemay be gradually increased at a desired rate so that the inflationprofile is substantially linear. FIG. 9 shows an inflation profile of afinger blood pressure cuff using a piezoelectric pump. As shown in FIG.9, the inflation rate of the inflation profile is approximately linear.By way of an example, increasing the duty cycle from 20% to 40% at 1%increase per second followed by increasing the duty cycle from 40% to60% at 0.5% increase per 0.1 seconds may achieve a substantially linearinflation profile.

A controller of the piezoelectric pump has adjusted one or more of aduty cycle, voltage, and drive frequency of the piezoelectric pump tocontrol the inflation rate of the piezoelectric pump. Not only doesadjusting parameters such as duty cycle, voltage, and/or drive frequencyreduce the inflation rate of the piezoelectric pump, but the inflationrate may be more linear.

Pressure Profile and Measurements of the Blood Pressure Cuff

OBPM systems measure a user's blood pressure by observing and analyzingoscillometric patterns in a pressure profile. In conventional OBPMsystems, the pressure profile is obtained by inflation of a bloodpressure cuff to a desired pressure to at least temporarily occludeblood flow in an underlying blood vessel, which is then followed bydeflation of the blood pressure cuff, with the cuff pressure being notedwhen the heartbeat is first registered again (for systolic pressure) andwhen the heartbeat ceases to be registered (for diastolic pressure). Atypical blood pressure measurement may inflate to an initial pressuregreater than the systolic blood pressure and then deflate to a finalpressure below the diastolic blood pressure. During the blood pressuremeasurement, a pressure profile may be recorded including one or morepulses that occur during inflation and deflation. The pulses are causedby the user's heartbeats. Techniques known in the art for determiningblood pressure from the one or more pulses recorded in a pressureprofile can be used.

In the present disclosure, a blood pressure cuff such as a finger bloodpressure cuff may be inflated in a first pressure profile to an initialpressure at least slightly above systolic pressure. At some point duringinflation, the bladder and the dermis will come into contact with enoughpressure that pulsations of blood in the dermis will be transmitted tothe bladder and evident as pressure pulsations measurable by thepressure sensor. These pulsations will generally increase in strength asthe dermis and bladder are pressed more firmly together, resulting inbetter coupling between the dermis and the bladder, up until the pointwhen the bladder exerts so much pressure through the dermis to theartery that blood flow stops (at which point the pulsations will alsocease. Generally speaking, the pressure at which pulsations in thedermis are first detectable by the pressure sensor have a correlation tothe person's diastolic blood pressure, whereas the higher pressure atwhich blood flow stops and the pulsations end generally have acorrelation to the person's systolic blood pressure. More particularly,typical oscillometric measurements may use the first and last pulsationsof a specific amplitude normalized to its maximum to ascertainmeasurements for diastolic and systolic blood pressure. Thus, ameasurement may typically involve inflating the cuff to a pressure abovethe systolic pressure and logging the pressure data that is measuredduring such pressurization. The systolic pressure may then be estimatedfrom information derived from the pressure data obtained duringinflation. The diastolic pressure may be estimated from informationderived from the pressure data obtained during deflation.

The blood pressure cuff of the present disclosure may more reliably andaccurately determine a person's blood pressure, including systolic anddiastolic pressure, by causing the pump to pressurize a pressurizablevolume of an inflatable bladder to a first pressure greater than amaximum amplitude pressure in a first pressure profile, and thensubsequently causing the pump to maintain the pressurizable volume at asecond pressure for a duration in a second pressure profile, where thesecond pressure is based at least in part on information from the firstpressure profile. The blood pressure cuff may include a controllercoupled to a pump in fluidic communication with the inflatable bladder,and coupled to a pressure sensor in fluidic communication with theinflatable bladder. The inflatable bladder defines, at least in part,the pressurizable volume. The pump is configured to pressurize thepressurizable volume and cause the inflatable bladder to contact auser's appendage when the pump is activated. The pressure sensor isconfigured to obtain and produce pressure data indicative of pressurewithin the pressurizable volume as a function of time, where thepressure data includes oscillometric data in the first pressure profileand pulse information in the second pressure profile. The first pressureprofile may be indicative of the pressure within the pressurizablevolume up to the first pressure as a function of time, and the secondpressure profile may be indicative of the pressure within thepressurizable volume as a function of time after reaching the firstpressure. In some embodiments, the second pressure profile is indicativeof the pressure within the pressurizable volume when the pressurizablevolume is maintained at the second pressure.

In order to obtain a cleaner signal and a more reliable estimate of aperson's blood pressure, in some implementations, the first pressureprofile may be approximately linear at a specific rate, such as betweenabout 1 mmHg per second and about 10 mmHg per second. In someimplementations, the first pressure profile may be non-linear, where thefirst pressure profile may be slower when approaching systolic pressureand diastolic pressure based on sensing pressure fluctuations. In someimplementations, the first inflation profile may include a steppedand/or slower inflation profile, where the stepped and/or slowerinflation profile may measure one or more of pulse wave analysis (PWA)features, arterial compliance, respiration, atrial fibrillation, andother physiological metrics.

In the present disclosure, the blood pressure cuff may undergo a processto record pressure data during inflation/deflation to a second pressureprofile subsequent to the first pressure profile. In the second pressureprofile, the blood pressure cuff may deflate from the first pressure tozero gauge pressure or other lower pressure and then re-inflate to asecond pressure as shown in FIG. 10. Alternatively, the blood pressurecuff may deflate from the first pressure to a second pressure as shownin FIG. 11. During the second pressure profile, the bladder may bemaintained at the second pressure for a sufficient duration to recordmultiple oscillations or pulsations originating from pulsative behaviorin the user's blood vessels. In some implementations, the appliedpressure may be held at the second pressure for a duration between about1 second and about 15 seconds, between about 3 seconds and about 10seconds, or between about 5 seconds and about 10 seconds. The secondpressure for the second pressure profile may be obtained frominformation in the first pressure profile. For example, the secondpressure can be a maximum amplitude pressure from oscillometric data(the oscillometric data referring to the oscillatory data that isproduced in the first pressure profile due to the pulsations in thesubject's blood vessels). Rather than continuously deflating orinflating past the second pressure after a first inflation process, thesecond inflation/deflation process can hold the applied pressure at thesecond pressure to obtain pulse information in the second pressureprofile. Pulse information may be used to extract and characterize oneor more of PWA features, arterial compliance, respiration, atrialfibrillation, and other physiological metrics. Since the pressure isconsistent in the second inflation/deflation process, pulses withsimilar amplitudes can be easily averaged to reduce noise and thereforemore robust features can be extracted. This may provide better data forpulse wave analysis. In some implementations, the pulse information fromholding the applied pressure at the second pressure can be used tovalidate information obtained from the first pressure profile.

FIG. 10 shows a graph for a blood pressure measurement depicting a firstpressure profile followed by a second pressure profile, where the secondpressure profile inflates to a targeted pressure and is held at thetargeted pressure; the targeted pressure, in this example, is themaximum amplitude pressure seen in the oscillometric data, which maycorrespond to the user's mean arterial pressure. The first pressureprofile shows a substantially linear inflation profile withoscillometric data being recorded during inflation. An applied pressurein the first pressure profile exceeds a maximum amplitude pressurerecorded from the oscillometric data. The maximum amplitude pressurecorresponds to the pressure at which the largest amplitude pressurechanges (reproduced below the first pressure profile). Pressure isreleased to deflate the blood pressure cuff to zero gauge pressure orapproximately zero gauge pressure. A second inflation follows where theblood pressure cuff is inflated to reach the targeted pressure, wherethe targeted pressure corresponds to the maximum amplitude pressuredetermined from the oscillometric data in the first pressure profile.The pressure is held or maintained at the targeted pressure, which canbe the user's mean arterial pressure. The pressure is held for aduration sufficient to produce pulse information in a second pressureprofile. The second pressure profile is recorded and shows asubstantially linear inflation profile with additional oscillometricdata (referenced to as pulse information, in this example) beingrecorded when the pressure is held at the targeted pressure. In someembodiments, systolic blood pressure and diastolic blood pressure can bedetermined from the pulse information in the second pressure profile.Inflections, peaks, and other features from the additional oscillometricdata or pulse information may be analyzed to extract more pulsefeatures.

FIG. 11 shows a graph for a blood pressure measurement depicting a firstpressure profile followed by a second pressure profile, where the secondpressure profile deflates to a targeted pressure and is held at thetargeted pressure. Similar to FIG. 10, the first pressure profile showsa substantially linear inflation profile with oscillometric data beingrecorded during inflation, where a pressure exceeds a maximum amplitudepressure recorded from the oscillometric data. Then the blood pressurecuff is deflated to reach a targeted pressure, where the targetedpressure corresponds to the maximum amplitude pressure determined fromthe oscillometric data in first pressure profile. The pressure is heldor maintained at the targeted pressure, which can be the user's meanarterial pressure. The pressure is held for a duration sufficient toproduce pulse information in a second pressure profile. The secondpressure profile is recorded, where additional oscillometric data(referenced to as pulse information, in this example) in the secondpressure profile is recorded when the pressure is held at the targetedpressure.

Position Detection of the Blood Pressure Cuff

The blood pressure cuff of the present disclosure may be equipped withone or more sensors to determine a relative position of the bloodpressure cuff with respect to a user's heart and/or, in some instances,an angular orientation of user's appendage that is inserted into thecuff relative to the earth's gravitational field. The one or moresensors may be coupled with a controller or control unit to receive datafrom the one or more sensors and determine whether the blood pressurecuff is properly positioned. In order to obtain an accurate bloodpressure measurement for a finger blood pressure cuff, a height of afinger to which the finger blood pressure cuff is attached is preferablylocated to be about the same height the user's heart. That way, theblood pressure measurement can factor out hydrostatic pressure that canotherwise lead to an inaccurate measurement.

In some implementations of the present disclosure, the blood pressurecuff may include one or more accelerometers. The one or moreaccelerometers may be used to estimate the relative position of theblood pressure cuff with respect to a user's heart and also to determinewhether the blood pressure cuff is in motion or not. When a user'sfinger is positioned within a finger blood pressure cuff, an angle ofthe finger blood pressure cuff may be determined to assist indetermining whether the user is holding the finger blood pressure cuffin the correct position. In some implementations, the one or moreaccelerometers are configured to measure an angle of the blood pressurecuff with respect to gravity. In some implementations, the one or moreaccelerometers may be used to measure inclinations, including a rollangle and a pitch angle, about axes that are orthogonal or substantiallyorthogonal to a vertical axis. The roll angle and the pitch angle may bewithin a threshold to assist in determining that the blood pressure cuffis positioned proximate to the user's heart. For example, each of thepitch angle and the roll angle may be between about 0 degrees and about30 degrees when the finger blood pressure cuff is positioned atapproximately the same elevation as the user's heart. The one or moreaccelerometers may be configured to measure acceleration in at least twoorthogonal directions or three orthogonal directions. Accelerationoutputs (A_(x), A_(y), and A_(z)) may be generated and provided to thecontroller, and the controller may use the acceleration outputs todetermine an inclination of the finger blood pressure cuff, where theinclination may be associated with the user's position of thehand/finger at an elevation of the user's heart.

FIGS. 12 and 13, for example, are photographs showing an example fingerblood pressure cuff depicted in earlier Figures as it may be worn duringa measurement, with the user placing their hand on their chest at anangle. This positioning generally results in the finger blood pressurecuff being at the same altitude as the person's heart. In someimplementations, a tri-axial accelerometer may be used to evaluateorientation of the finger blood pressure cuff relative to the earth'sgravitational field. The finger blood pressure cuff may check forangular orientation with respect to all three axes to determine whetherthe user's forearm (or, more precisely, the user's finger) is at anangle between 15° and 45° from a horizontal axis, and whether a base (orother predefined reference surface) of the finger blood pressure cuff isapproximately parallel to a vertical axis. For example, determiningwhether the base is approximately parallel to the vertical axis can meanthat the base is parallel to a plane that is between about 75° and about105° C. from the vertical axis. In other words, the finger bloodpressure cuff may view a range of angular orientations as being withinacceptable bounds for such a determination as being approximately thesame altitude as the user's heart, e.g., with the bottom or base of theapparatus within ±15° of vertical and the centerline of the apparatus(the centerline of the bladder/opening) at 30°±15° of horizontal. Whensuch a determination is made by the accelerometer, the finger bloodpressure cuff may activate the pump to inflate an inflatable bladder toinitiate a process for obtaining a blood pressure measurement.

In addition or in the alternative, the blood pressure cuff may includeone or more altimeters. The one or more altimeters may detect changes inaltitude and may be configured to determine an elevation of the bloodpressure cuff with respect to a user's heart. In some implementations,the one or more altimeters may measure the change in elevation inresponse to changes in angle of the blood pressure cuff, and may be usedto instruct the user to reach the correct level (e.g., “lower your handby 2 inches”).

In addition or in the alternative, the blood pressure cuff may includeone or more auscultation sensors to acoustically determine a location ofthe user's heart. In some implementations, the one or more auscultationsensors include a microphone to listen for a user's heartbeat anddetermine proximity to the user's heart accordingly. Thus, the one ormore auscultation sensors may be used as one or more proximity sensorsto determine whether the blood pressure cuff is positioned proximate tothe user's heart.

In addition or in the alternative, the blood pressure cuff may includeone or more optical sensors for determining that the user's finger ispositioned within a hole of the blood pressure cuff. As discussed above,the material of the inflatable bladder may be transparent orsubstantially transparent to certain wavelengths of light. The one ormore optical sensors may be incorporated within the finger bloodpressure cuff or, more specifically, within the inflatable bladder. Theone or more optical sensors may be configured to detect whether a user'sfinger has been inserted through the hole of the blood pressure cuff. Insome implementations, the one or more optical sensors may include one ormore photoplethysmographic (PPG) sensors. The one or more PPG sensorsmay be used to determine at least one of a user's heart rate,respiration rate, skin condition, or other physiological metrics.

In some implementations, the one or more accelerometers or other motionsensors may be used to determine whether the blood pressure cuff is inmotion or not. The blood pressure cuff may be configured to not initiatea blood pressure measurement and inflate the elastic bladder of thefinger blood pressure cuff while the finger blood pressure cuff is inmotion. When the blood pressure cuff is properly positioned at theelevation of the user's heart and measured motion is low enough for asufficient duration, a blood pressure measurement may be initiated. Thecontroller may automatically initiate inflation of the inflatablebladder when the one or more motion sensors (e.g., one or moreaccelerometers) determine that the finger blood pressure cuff ispositioned within a threshold elevation of the user's heart orpositioned proximate to the user's heart for a sufficient duration. Asufficient duration may be between about 0.5 seconds and about 5 secondsor between about 1 second and about 3 seconds. For example, a thresholdelevation may be within ±2 inches of the user's heart, or within atargeted angular orientation as described above.

In some implementations, the controller may be configured to turn offthe blood pressure cuff or enter a power-saving mode when the bloodpressure cuff is motionless or stationary for a threshold duration andthe one or more motion sensors determine that the device is notpositioned within the threshold elevation of the user's heart. Thecontroller may automatically turn off the blood pressure cuff or enter apower-saving mode when the one or more motion sensors determine that thefinger blood pressure cuff has been motionless for a threshold duration,where a threshold duration may be between about 5 seconds and about 1minute or between about 10 seconds and about 30 seconds. In someimplementations, the sufficient duration and/or threshold duration maybe defined by a user. In some implementations, the blood pressure cuffmay be configured to turn off or enter a power-saving mode when thefinger blood pressure cuff is oriented in a manner with respect togravity to indicate that the finger blood pressure cuff is not in use.For example, the controller may automatically turn off the finger bloodpressure cuff or enter a power-saving mode when the one or more motionsensors determine that a substrate or flat surface (e.g. base) of theblood pressure cuff is oriented orthogonally with respect to gravity.

FIGS. 14 and 15 show photographs of an example finger blood pressurecuff resting on a surface and with a finger inserted through an openingof the finger blood pressure cuff to take a blood pressure measurement.When the finger blood pressure cuff is resting on the surface as shownin FIG. 14, a pump is not activated to inflate an inflatable bladder. Insome implementations, the finger blood pressure cuff may be configuredto turn off or enter a power-saving mode when resting on the surface fora long enough duration. Regardless of whether the finger blood pressurecuff is resting on a surface or not, a user's finger may be insertedthrough an opening of the finger blood pressure cuff as shown in FIG.15. In some implementations, a pump is activated to cause inflation ofan inflatable bladder to make contact around the user's finger. Thefinger blood pressure cuff may be configured to take a blood pressuremeasurement when the user's finger is inserted through the opening andthe inflatable bladder is inflated to contact the user's finger. Whilethe finger blood pressure cuff can be used to take a blood pressuremeasurement with the finger blood pressure cuff resting on a surface, itwill be understood that the finger blood pressure cuff can be used totake a blood pressure measurement when the finger blood pressure cuff isnot resting on a surface. In some implementations, more accurate bloodpressure measurements can be taken when the finger blood pressure cuffis positioned at the same or substantially the same elevation as theuser's heat or positioned proximate to the user's heart.

In some implementations of the present disclosure, the blood pressurecuff may include one or more proximity sensors. The one or moreproximity sensors may be configured to determine whether the bloodpressure cuff is proximate to a user's heart or not. In addition or inthe alternative, the one or more proximity sensors may be configured todetermine whether the user's appendage (e.g., user's finger) is properlypositioned in the blood pressure cuff. Examples of proximity sensors mayinclude capacitive, optical, and photoelectric sensors. The one or moreproximity sensors may be used to detect the presence of a user's chest,skin, body, or finger. In some implementations, the blood pressure cufffurther includes one or more motion sensors to determine whether thedevice is in motion or stationary. In some implementations, the bloodpressure cuff further includes a controller configured to initiateinflation of the inflatable bladder using a pump when the one or moreproximity sensors determine that the blood pressure cuff is positionedproximate to the user's heart and when the one or more motion sensorsdetermine that the device is stationary for a sufficient duration.

In some implementations, the one or more proximity sensors include oneor more auscultation sensors configured to acoustically determineproximity to the user's heart. The one or more auscultation sensorsfunction as a stethoscope to listen for a user's heartbeat and determineproximity to the user's heart. The one or more auscultation sensors caninclude a microphone that acts as the proximity sensor to acousticallydetermine a location of the user's heart, thereby assisting in properpositioning of the blood pressure cuff prior to making a blood pressuremeasurement.

In some implementations of the present disclosure, the blood pressurecuff may further include one or more feedback devices. The one or morefeedback devices may be configured to communicate positioning of theblood pressure cuff relative to the user's heart and/or positioning ofthe user's finger relative to the opening of the blood pressure cuff.Feedback from the one or more feedback devices may include communicatingto the user that a blood pressure measurement is occurring, that a bloodpressure measurement is complete, that the elastic bladder is inflating,that the elastic bladder is deflating, whether the blood pressure cuffis properly positioned or not, whether the user's finger is properlypositioned or not, information regarding physiological data associatedwith the user such as systolic pressure, diastolic pressure, meanarterial pressure, heart rate, respiratory rate, and blood pressure riskzone/information. The one or more feedback devices may include but isnot limited to a speaker for audio feedback, light-emitting diodes (LED)for optical feedback, a display for visual feedback, andmotor/vibramotor for haptic feedback. In some implementations, the oneor more feedback devices may include a display to present visualfeedback to the user. The display (e.g., screen) may display guidance,user, connectivity, biometric data, and/or blood pressure results to theuser. In some implementations, the one or more feedback devices mayinclude a speaker and/or microphone for audio control and guidance. Insome implementations, the blood pressure cuff includes an interface forreceiving any or all of the aforementioned feedback by way of one ormore intermediary devices (from one device to another), such as from asmartphone, a wearable device, computer, or remote server. In someimplementations, a remote device such as a smartphone, wearable device,computer, or remote server may provide any or all of the aforementionedfeedback directly to the user.

Other Embodiments

There are many concepts and embodiments described and illustratedherein. While certain embodiments, features, attributes, and advantageshave been described and illustrated herein, it should be understood thatmany others, as well as different and/or similar embodiments, features,attributes and advantages are apparent from the description andillustrations. As such, the above embodiments are merely provided by wayof example. They are not intended to be exhaustive or to limit thisdisclosure to the precise forms, techniques, materials and/orconfigurations disclosed. Many modifications and variations are possiblein light of this disclosure. It is to be understood that otherembodiments may be utilized and operational changes may be made withoutdeparting from the scope of the present disclosure. As such, the scopeof the disclosure is not limited solely to the description above becausethe descriptions of the above embodiments have been presented for thepurposes of illustration and description.

As used herein, terms such as “about,” “approximately,” “nominally,” andthe like with respect to numerical values or relationships, e.g.,perpendicularity or parallelism, are to be understood to include, unlessotherwise indicated, the value or relationship indicated ±10% of thatvalue or relationship (e.g., for approximately parallel, the value maybe 90°±9°).

The present disclosure is neither limited to any single aspect norembodiment, nor to any combinations and/or permutations of such aspectsand/or embodiments. Moreover, each of the aspects of the presentdisclosure, and/or embodiments thereof, may be employed alone or incombination with one or more of the other aspects and/or embodimentsthereof. For the sake of brevity, many of those permutations andcombinations will not be discussed and/or illustrated separately herein.

What is claimed is:
 1. A device for estimating a user's blood pressure,the device comprising: an inflatable bladder defining, at least in part,a pressurizable volume; a pump in fluidic communication with theinflatable bladder and configured to pressurize the pressurizable volumeand cause the inflatable bladder to inflate and contact a user'sappendage when the pump is activated; a pressure sensor in fluidiccommunication with the inflatable bladder and configured to producepressure data indicative of pressure within the pressurizable volume asa function of time; and one or more accelerometers, wherein the one ormore accelerometers are configured to determine relative positioning ofthe device with respect to a user's heart.
 2. The device of claim 1,wherein the inflatable bladder is an inflatable elastic bladder disposedabout an inward-facing surface of a hole in the device, wherein the pumpis configured to pressurize the pressurizable volume when a user'sfinger is positioned in the hole of the device.
 3. The device of claim1, wherein the one or more accelerometers are further configured todetermine whether the device is in motion or stationary.
 4. The deviceof claim 3, further comprising: a controller configured to initiateinflation of the inflatable bladder using the pump when the one or moreaccelerometers determine that the device is positioned within athreshold elevation with respect to the user's heart and is stationaryfor a threshold duration.
 5. The device of claim 4, wherein thecontroller is further configured to turn off the device or enter apower-saving mode when the one or more accelerometers determine that thedevice is not positioned within the threshold elevation with respect tothe user's heart and is stationary for a sufficient duration.
 6. Thedevice of claim 1, wherein the one or more accelerometers are configuredto determine relative positioning of the device with respect to a user'sheart by measuring an inclination about an axis that is orthogonal orsubstantially orthogonal to a vertical axis, the inclination including aroll angle and a pitch angle, wherein each of the roll angle and thepitch angle is between about 0 degrees and about 30 degrees when thedevice is determined to be at approximately the same elevation as theuser's heart.
 7. The device of claim 1, further comprising: one or morealtimeters configured to determine an elevation of the device withrespect to the user's heart.
 8. The device of claim 1, furthercomprising: one or more auscultation sensors configured to acousticallydetermine a location of the user's heart.
 9. The device of claim 1,further comprising: one or more optical sensors for determining that theuser's finger is positioned within a hole of the device, wherein theinflatable bladder is disposed about an inward-facing surface of thehole of the device.
 10. The device of claim 1, further comprising: oneor more feedback devices configured to communicate to a user apositioning of the device relative to the user's heart, wherein the oneor more feedback devices include at least one of a speaker for audiofeedback, a light-emitting diode (LED) for optical feedback, a displayfor visual feedback, and a motor for haptic feedback.
 11. The device ofclaim 10, wherein the one or more feedback devices are furtherconfigured to communicate to the user that a blood pressure measurementis occurring.
 12. A device for estimating a user's blood pressure, thedevice comprising: an inflatable bladder defining, at least in part, apressurizable volume; a pump in fluidic communication with theinflatable bladder and configured to pressurize the pressurizable volumeand cause the inflatable bladder to inflate and contact a user'sappendage when the pump is activated; a pressure sensor in fluidiccommunication with the inflatable bladder and configured to producepressure data indicative of pressure within the pressurizable volume asa function of time; and one or more proximity sensors, wherein the oneor more proximity sensors are configured to determine that the device ispositioned proximate to a user's heart.
 13. The device of claim 12,wherein the inflatable bladder is an inflatable elastic bladder disposedabout an inward-facing surface of a hole in the device, wherein the pumpis configured to pressurize the pressurizable volume when a user'sfinger is positioned in the hole of the device.
 14. The device of claim12, wherein the one or more proximity sensors include one or both of anauscultation sensor and a microphone configured to acousticallydetermine proximity of the user's heart.
 15. The device of claim 12,wherein the one or more proximity sensors include one or more opticalsensors configured to determine proximity to a user's chest anddetermine a presence of a user's finger in a hole of the device.
 16. Thedevice of claim 12, further comprising: one or more accelerometersconfigured to determine whether the device is in motion or stationary.17. The device of claim 16, further comprising: a controller configuredto initiate inflation of the inflatable bladder using the pump when theone or more proximity sensors determine that the device is positionedproximate to the user's heart and the one or more accelerometersdetermine that the device is stationary for a threshold duration. 18.The device of claim 17, wherein the controller is further configured toturn off the device or enter a power-saving mode when the one or moreproximity sensors determine that the device is not positioned proximateto the user's heart and the one or more accelerometers determine thatthe device is stationary for a sufficient duration.
 19. The device ofclaim 12, further comprising: one or more feedback devices configured tocommunicate to a user a positioning of the device relative to the user'sheart, wherein the one or more feedback devices include at least one ofa speaker for audio feedback, a light-emitting diode (LED) for opticalfeedback, a display for visual feedback, and a motor for hapticfeedback.
 20. The device of claim 19, wherein the one or more feedbackdevices are further configured to communicate to the user that a bloodpressure measurement is occurring.